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| Titel |
An aeromagnetic double cover of Karasjok, Norway |
| VerfasserIn |
M. Brönner, K. Fabian, A. Nasuti, S. A. McEnroe |
| Konferenz |
EGU General Assembly 2012
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 14 (2012) |
| Datensatznummer |
250067652
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| Zusammenfassung |
| Separating remanent from induced magnetic anomalies is a challenging but important task in
the interpretation of aeromagnetic data. A comprehensive knowledge of petrophysical
properties and geological processes is necessary to estimate the quantity and distribution of
remanent rocks in an area to obtain a realistic model. A different and more efficient
possibility to achieve this separation is to use repeated high-quality aeromagnetic
measurements, performed within diverse geomagnetic fields. If the geomagnetic field
substantially changed between two surveys, A and B, due to the regional geomagnetic
secular variation, the difference between both survey anomalies mainly results from the
magnetization induced by this secular variation ΔH = HB - HA. In many places of the
world the secular variation during the last 30 years has been more than 500Â nT, giving a
sufficiently high signal-to-noise ratio in the difference of two high-quality data sets. Here a
double cover of a continental magnetic anomaly near Karasjok, northern Norway, is studied
using two surveys of similar resolution made in 1982 and in 2011 covering a common area of
20 km à 30 km. An evaluation of IGRF models confirms that the geomagnetic field
intensity in this region has increased by approximately 500Â nT. In the case of a
purely induced magnetization, the anomaly amplitudes should have consistently
increased by about 1% in response to the field increase. Deviations from this expected
variation make it possible to identify remanent magnetic anomalies in crustal rocks, a
topic of high relevance with respect to mineral exploration and lamellar magnetism. |
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